Logical Operators

Arguments

Returns

Non-nil or nil.

Description

In Gamma or Lisp, any expression which is not nil is treated as being true (t) for the purpose of boolean logic. Applying ! to any non-nil expression will produce nil. Applying ! to nil must produce an arbitrary non-nil result. The generic non-nil value in Gamma is t.

&& evaluates each of its arguments in order, and continues so long as each argument evaluates to non-nil. If any argument is nil, then nil is returned immediately, without evaluating the rest of the arguments. If no argument is nil, the last argument is returned.

|| returns non-nil if any of its arguments is not nil. Each argument is evaluated in turn, and as soon as a non-nil value is reached, that argument is returned. Subsequent arguments are not evaluated.

Examples

    Gamma> 6;
    6
    Gamma> !6;
    nil
    Gamma> !nil;
    t
    Gamma> 5<6 && string("hi ","there");
    "hi there"
    Gamma> 5>6 && string("hi ","there");
    nil
    Gamma> x = 5;
    5
    Gamma> y = 6;
    6
    Gamma> (x = t) || (y = 0);
    t
    Gamma> x;
    t
    Gamma> y;
    6
    Gamma> 
    		

See Also

and, not, or